New methods, in particular a two-compartment box and a T-maze for shock avoidance, will be added to the continuing use of lever-pressing shock-escape and food-approach procedures for rapidly training rats to discriminate different drug conditions. Conditions used as discriminative stimuli will include intravenous infusion of small doses of morphine, testing within a few seconds after administration in order to study the immediate, possibly euphoric sensation. Ongoing studies will be continued and extended on discrimination between different drugs and on synergism and antagonism between drugs. Tolerance and minimal detectable doses will also be tested. Biochemical assay methods will be used to measure the amounts of drug in the brain and the effectiveness of experimental manipulations of acetylcholine and other endocrinological substances to be related to the discriminability of drug effects. Prior research on effects of drug on dominant-attack and subordinate- defensive behavior in rats will be extended by testing chronic effects of delta9-tetrahydrocannabinol and of other drugs.